Interleaving
Mix topics in one session — don’t block them.
What the Research Says
Most students revise by blocking — an hour on algebra, an hour on geometry, an hour on statistics. It feels productive and the topic seems clear by the end. Interleaving is the opposite: you jump between topics inside a single session. It feels worse at the time, and you’ll make more mistakes. But when the real exam arrives, you will be dramatically better at knowing which technique to apply — and that is usually the hardest part of any exam question.
Evidence Base
| Study | Finding | Impact |
|---|---|---|
| Rohrer & Taylor (2007) | Students who interleaved maths topics scored 43% higher on delayed tests than blocked-practice students. | Same time spent — huge difference in exam performance. |
| Birnbaum et al. (2013) | Interleaved learners felt LESS confident during practice but performed BETTER in the test. | If revision feels too easy, interleave. |
| Bjork & Bjork (2011) | Desirable difficulties — including interleaving — create durable long-term learning at the cost of short-term performance. | Short-term struggle is the price of long-term gain. |
| Taylor & Rohrer (2010) | Benefit was largest when topics looked superficially similar — students learnt to DISTINGUISH them. | Most useful where students confuse similar techniques. |
Step-by-Step Method
- 1Pick 3–5 related topics — topics that share a paper, a theme, or a question type. Similar enough that students confuse them.
- 2Make a mixed problem set — 10–15 questions drawn randomly from all the topics. Don’t tell yourself which topic each question belongs to.
- 3Attempt each question cold — first step is identifying what’s being asked. That identification is the skill you’re training.
- 4Mark after every question — note which topic each one was. Pay attention to mis-identifications — those are the highest-value gaps.
- 5Rebuild a new mixed set tomorrow — same topics, different questions. Different order. Over time, misclassifications drop.
- 6Expect to feel worse than blocked practice — that’s the right feeling. Your exam self will thank you.
Mix materials, mechanical calculations, and named-designer questions in one 45-minute session: a gear-ratio calculation, a question on the properties of softwood versus hardwood, then a describe-and-evaluate question on Dyson’s design approach. The key exam discrimination skill is identifying which topic area Q6 is targeting — interleaving builds exactly that recognition before you see the paper.
Create a mixed set of short-answer cards covering smart materials (thermochromic, piezoelectric), electronic components (input–process–output examples), and sustainability (6 Rs, lifecycle assessment) and shuffle them randomly. Attempt 12 in 20 minutes. Students who block “smart materials” for a whole session find they can answer those questions but freeze when a mixed exam question requires switching between topic areas.
Common Pitfalls
- Random, not related. Interleaving Design and Technology with Maths is just subject-switching. Interleave WITHIN a subject — related topics that students confuse.
- Giving up when it feels hard. The discomfort is the signal that it’s working. Don’t revert to blocked practice because interleaving feels slow.
- Labelling the topic at the top of each question. Defeats the point — the identification IS the training.
- Using it too early in learning. You need baseline familiarity with each topic first. Interleaving is for consolidation, not first exposure.
When to Use This
Once you’ve covered a handful of related topics — usually partway through a term — start weaving them into mixed practice sessions. Very useful in the final 8–10 weeks before exams when you’re moving from learning to applying. Full past papers are the ultimate interleaving exercise, because they force you to identify question types cold.